The present invention relates to a wheel alignment control method for a motor vehicle and a control apparatus therefor, and more particularly, to a control method and a control apparatus for establishing wheel alignment adaptable to a vehicle drive state by making a fine adjustment for wheel alignment.
A motor vehicle may be put in various situations, such as a state in which it is driven at a very low speed, a state in which it runs in an urban district or on a thruway or mountain road, etc. In other words, there are various vehicle drive modes. With respect to steering operation, moreover, there are various steering modes associated with the frequency of the steering operation, troublesomeness of the steering operation a driver feels, and the like. Thus, the vehicle drive state (vehicle drive mode and steering mode) variously changes, and optimum wheel alignment varies depending on the vehicle drive state.
In order to achieve the wheel alignment properly, as is conventionally known, it is automatically adjusted in accordance with the behavior of the vehicle detected during the vehicle drive or the vehicle drive state. Proposed in Japanese Patent Provisional Publication No. 5-32114, for example, is a control method in which camber angle adjusting means attached individually to front and rear wheels of a vehicle are independently controlled in accordance with the transverse acceleration of the vehicle, which is indicative of the vehicle behavior, whereby the camber angle and, therefore, wheel alignment can be controlled. Proposed in Japanese Patent Provisional Publication No. 60-193781, moreover, is a method in which a vehicle velocity indicative of the vehicle behavior is detected, and the camber angle is changed to the negative side when the vehicle velocity exceeds a predetermined level. Described in Japanese Patent Provisional Publications Nos. 59-67111 and 62-55205, furthermore, are a method in which the caster angle is increased in a high-velocity region, and a method in which the toe angle is controlled so as to be adaptable to the vehicle velocity, respectively.
According to the prior art methods described above, the camber angle, caster angle, or toe angle, and therefore, the wheel alignment is variably adjusted in accordance with the vehicle transverse acceleration or change of vehicle velocity, which is indicative of the vehicle behavior. Accordingly, the wheel alignment can be adjusted in some measure to the vehicle drive state as well as the vehicle behavior.
Since the vehicle drive state changes variously, however, it is generally difficult to establish optimum wheel alignment for the drive state at all times. According to some of the individual prior art methods described above or combinations thereof in which the vehicle drive state is discriminated by the transverse acceleration or vehicle velocity, for example, the vehicle drive state, which changes variously as aforesaid, cannot be detected properly, so that it is hard to establish the optimum wheel alignment.